I doubt a list like that exists, as each place that might allow them also might have several restrictions on when you can use them and where you can use them.
Here is just one example of a campground in the Smokies (Elkmont), that allows them, but not on all sites an not at all times.
"Quiet hours are in effect from 10:00 p.m. to 6:00 a.m.
Generator use is restricted to 8 a.m. to 8 p.m. Generators may not be left running unattended.
Generator use is prohibited from May 15 through October 31 in loops A, B, L, M and N."
I suspect the best way to find up-to-date information on whether a campsite allows generators is to call them and ask or see if they list any info on their website.